The sensing of analytes (such as chemical warfare agents, etc.) with considerable sensitivity and specificity is a requirement in many circumstances. Sensitivity is required to sense analytes before their level reaches an undesired value. Specificity is necessary to avoid false positives that would engender unnecessary, costly, and potentially dangerous responses.
Chemical warfare agents are lethal compounds applied to warfare have been developed over many years, some derived from commercial compounds used to control destructive animals, insects, and plants, others are toxic industrial chemicals, such as chlorine, that also have been used in warfare. Still others are the product of military research and development intended to produce lethal agents of desired characteristics and effects.
The complexity and variety of chemical compounds, many only slightly different in structure or chemical reactivity, make the task challenging. False positive such as may originate from similar compounds present in the sampled environment are a source of concern.
For detecting certain molecules (such as chemical warfare agents, etc.), there are various conventional sensors and detectors that have been previously provided. However, these existing sensors and detectors are not without flaws and shortcomings. For one, there is wanted greater sensitivity, namely, the ability to detect on the order of parts per trillion (ppt).
Significantly, current sensors and detectors tend to have a false alarm (false positive) problem, namely, that the sensors and detectors are triggered not just by what is wanted to be detected but also triggered by “interferents.” For example, in the case of current sensors used by the chemical agent detector community, benzene and toluene are potential interferents. These chemicals are components of JP-8 and diesel fuel vapors and exhaust and associated with a variety of burning materials and gunfire. False alarm problems have been reported in the testing of currently used fieldable chemical agent detectors in the presence of JP-8 and diesel vapor and exhaust, as well as toluene. In these tests a positive detection of either nerve or blister agents was registered when neither of these chemical warfare agents was present.
Another example where sensitivity and specificity are needed is in sensing compounds in the environment that are destructive to the atmosphere and water and endanger the health of those exposed. In other cases chemical sensing is important for the collection of information about criminal and foreign military developments and operations. In industrial operations, chemical sensing is necessary to recognize when dangerous processes may be incompletely contained, becoming uncontrolled, and/or potentially creating a HAZMAT release.
There have not yet been provided, but are wanted, fieldable devices with sensors that are both sufficiently sensitive and versatile to provide for detection of a variety of important threat agents and simultaneously discriminating of, or insensitive to, interferents which would register false positives.
Also, there are needs for detecting toxic materials in water samples. The safety of drinking water is of importance for military deployments in combat zones. Domestically there is the treat of terrorist attacks against water supply systems. A large concern is the protection of populations against toxic chemicals that find their way into drinking water, and into lakes, rivers, bays and oceans where they harm animals and fish, and damage recreational uses of such natural resources.